Spectator sport … fans watch the big screen in the Olympic Park. But will people take up the torch and get active themselves? Photograph: Jeff J Mitchell/Getty Images

The Olympic legacy has promised to create a "healthier, happier, more active nation", so it's ironic that I spent more time in the last fortnight sitting on my bum glued to the TV than ever before. But not, perhaps, as ironic as the government's failure thus far to capitalise on the current wave of enthusiasm for sport with a cohesive strategy for promoting physical activity.

"While 'sport' belongs to the Department of Culture Media and Sport, 'exercise or physical activity' is seen as being within the remit of the Department of Health,' says David Stalker, CEO of the Fitness Industry Association (FIA). Hugh Robertson, the minister for sport, openly declared that his interest was in increasing participation rather than improving the nation's health, leading Lord Krebs, the chairman of the committee, to state: "Government is failing to act in a consistent way to ensure that the Olympics help us tackle one of our greatest health threats – sedentary lifestyles."

If you are in any doubt about the magnitude of the problem, consider the findings of a study published last month in the Lancet that concluded physical inactivity was responsible for 6-10% of cases of heart disease, type 2 diabetes, breast and colon cancer globally – and 9% of premature deaths. This, the authors suggest, makes a sedentary lifestyle as serious a threat to health and longevity as smoking. The Lancet also revealed that we in Britain are among the most slothful nations in the developed world, with 63.3% of us failing to meet the recommended physical activity guidelines.

So why, given the compelling evidence of a clear dose-response relationship between physical activity and disease, have we failed to recognise and promote the role of physical activity both in the prevention and treatment of chronic disease?

One possible reason, believes sports and exercise medicine consultant Dr Richard Weiler, is the lack of emphasis on physical activity and its benefits in British medical schools. Weiler's research, published in the British Journal of Sports Medicine this month, found that 44% of medical schools did not teach trainee doctors the national exercise guidelines, and that on average a paltry 4.2 hours was devoted to education on physical activity. In separate research, a survey of 48 London GP practices revealed that none knew the latest physical activity guidelines.

"There is an urgent need for physical activity teaching to have dedicated time at medical schools, to equip tomorrow's doctors with the basic knowledge, confidence and skills to promote physical activity," says Weiler.

Stalker agrees. "Two-thirds of the population isn't doing enough exercise and 83% of the population goes to their GP every year," he says. "So it is a case of GPs understanding that although not all of this 83% have a chronic condition, physical inactivity is a major risk factor for disease and they need to have the confidence to make recommendations and referrals to exercise."

The Lords committee identified lack of awareness and inadequate training among health professionals as a key barrier preventing the treatment of ill health by exercise, as well as a lack of confidence in exercise referral schemes.

But Stalker says change is afoot. "The Royal College of Physicians called for the development of clear standards outlining the process by which a doctor can refer a patient to an exercise programme," he explains. "This work is underway, led by a joint consultative forum between the medical profession and exercise sector and represents the first time these sectors have worked together."

Dr Andrew Murray, the recently appointed "physical activity champion" for the Scottish government, says steps are already being taken in Scotland. "They've really grasped the importance of this issue up here," he says. Murray is working closely with Scotland's chief medical officer to promote physical activity with the aims of increasing life expectancy and decreasing the incidence of chronic disease. The more immediate goal is to increase the percentage of Scots meeting the guidelines from 39% currently to 50% by 2022.

How? A ministerial debate on obesity and physical activity held in the Scottish parliament in May led to pledges from Shona Robison, minister for Commonwealth Games and sport, to maintain the physical activity budget of £3.3m for the next three years, to make £6m available to local authorities to help them achieve the "two hours of PE per week" target, and to increase funding for sustainable transport initiatives including walking and cycling. Meanwhile, NHS Scotland has just released a series of free online educational tools for its staff to learn how best to broach the subject of physical activity and motivate and support people to get active. "We need to get the message across that physical activity is not only important by itself, it can also offset the symptoms of many obesity-related conditions, such as diabetes and osteoarthritis," says Murray.

While Stalker believes that educating healthcare professionals will make a difference, he is keen to see other action. "There is an argument for placing an exercise professional or someone qualified to delivery physical activity counselling within GP surgeries to offer support in identifying patient pathways for exercise," he says. "Equally important is ensuring that physical activity is represented within the Quality Outcomes Framework (QOF), which is the system incentivising GPs to prescribe certain treatments."

This was one of the recommendations made the by Lords report, along with support for appropriate training both at undergraduate level and in continuing professional development of health professionals, in prescribing exercise as a preventative measure and treatment for chronic diseases.

The committee also recommended that the National Institute for Health and Clinical Excellence (Nice) assesses the research on the use of exercise in the management of chronic diseases and, where the evidence supports it, update their guidelines to reflect these findings. This could lead to a scenario where a GP assesses a patient and decides the most appropriate treatment for their high blood pressure is physical activity rather than drugs.

While it is encouraging to see a more committed attitude to physical activity from the government, Dr Weiler stresses the importance of a coordinated approach. "We need the same type of strategy that was used for smoking cessation," he says. That campaign went far beyond telling people smoking was bad for them: it also entailed supporting their efforts to stop on a practical level and using legislation to make not smoking easier than smoking.

"One of the problems is that our environment is not designed to encourage physical activity," says Weiler. In offices, shopping centres and other public buildings, lifts and escalators take centre stage, with dingy staircases round the back – out of sight and out of mind. Yet the Lancet study found that campaigns using motivational signs, such as those directing people to stairs instead of lifts, were among the most successful. Exactly this type of signage has been used in London throughout the Olympics – presumably as much to ease the strain on the city's public transport system as to boost the nation's health – but all the same, I'd like to see it remain.

Fred Turok, the FIA's chairman, chairs the government's Responsibility Deal physical activity network, which works to encourage businesses to promote physical activity among employees – emphasising the knock-on effect that a healthier workforce has on productivity and profitability. "It's not just about gyms at the office," he says. "It's about enabling employees to be more active: providing showers, prioritising stairs over lifts or promoting active commuting – walking, running or cycling to work." That's all for the good, as long as employees embracing the "move more, more often" message don't get made to feel like slackers when they spend their allotted lunch hour taking a walk or hitting the gym.

Even though the government is finally acknowledging what the fitness industry has been saying for decades – that physical activity matters – it's not yet clear whether the sofa-bound British public will buy into it this time around. Stalker is optimistic. "I think the reaction we have seen to this summer's Olympic Games, coupled with a backdrop of rising levels of obesity and a health service at breaking point, have driven people towards the realisation that they cannot put off getting active any longer," he says.

Weiler agrees. "We can't carry on doing nothing about it. The cost of doing so will far outweigh the investment required to increase physical activity levels and prevent this public health crisis."